POW Cards were an accessory produced by Doc's Games/Uncle Morty Productions, presumably for use with their line of tiny role-playing games (Dinky Dungeons being the best-known of these).
Set #1 contains 17 cards with sound effects (POW!, BONK!, BOOM!, etc.) rendered in a elaborated older comic-book style. It also contains 10 blank cards, presumably for the creation of one's own effects.
Their exact intended use is currently unknown. The Doc's Games catalog describes them as "The role playing aid no one's talking about."